A contact lens of this type is generally known.
A known bifocal contact lens, which is available on a small scale, has a curved shape which as far as possible corresponds to the shape of the eye of the wearer. Seen from the front, this contact lens is circular and is provided with a concentric optical zone, which is subdivided into concentric circular layers. In a bifocal lens, the concentric layers have, turn and turn about, a first and a second focal point. In these contact lenses the so-called diffractlye or simultaneous system is used, with which a first image, for example a distant image, is formed by the layers having the first focal point and, at the same time, a second image, for example the reading image, is formed by the layers having the second focal point. This principle is based on the concept that people are capable of separating these images in the brain and of concentrating on one of the two images. When the contact lens wearer wishes to see a distant object, he or she concentrates on the image of the object. The image which this person discerns through the layers having the second focal point is unsharp and blurred, which could assist in concentrating on the first image. It should be possible to apply the corresponding reasoning in the case of a reading image.
However, the known bifocal contact lens has the disadvantage that losses in contrast arise, inter alia as a consequence of the double images. Moreover, it has been found that only a few people have the above-mentioned ability to separate images, with the result that acceptance of the known bifocal lens in practice was highly disappointing.